The invention relates to a lamp of the type having a protective sleeve of quartz surrounding a light source, in particular a metal halide arc tube having a pair of opposed leads. The sleeve is supported by a metal frame comprising a pair of metal frame members which also supply current to the leads.
Protective sleeves of quartz or other transparent material able to withstand operating temperatures are commonly utilized around metal halide arc tubes, also known as high intensity discharge or HID arc tubes, in order to provide protection against non-passive failure during lamp operation. These sleeves act to slow or stop fast moving arc tube fragments and prevent the rupture of the outer lamp envelope. These sleeves may also provide other functions including, but not limited to, reduction of the UV output of the lamp.
Protective sleeves are typically mounted around the arc tube using additional straps or clips around the outside or in the ends of the sleeve. In the case of quartz metal halide arc tube, any metal supports used in the mounting must be kept away from the arc tube or be electrically floating to reduce the rate of sodium loss. An arrangement of this type, having a metal frame member outside of the sleeve, is disclosed in EP 0 784 334.
A known floodlamp having a parabolic aluminized reflector (PAR) utilizes a metal halide arc tube and a protective sleeve supported by straps attached to current carrying wire frame members outside the sleeve. The frame members are brazed into metal ferrules at the base of the reflector, and therefore must have good alignment.
U.S. Pat. No. 5,719,463 discloses a metal halide discharge lamp having a quartz metal halide arc tube with a quartz protective sleeve. A first lead wire for the arc tube passes through the inside of the sleeve and is provided with insulation to prevent sodium loss from the arc tube. This lead wire engages a dimple in the top of the ellipsoidal outer envelope to provide stability. The protective sleeve is supported by insulated stop members fitted in opposed ends of the sleeve and around the first lead wire. One of the stop members is held in place by a bend in the first lead wire, while the other is held in place by a bend in the second lead wire.
U.S. application Ser. No. 09/135,863 discloses a metal halide discharge lamp having a ceramic metal halide arc tube with a quartz protective sleeve. A first lead wire passes through the sleeve and engages a dimple in the outer envelope, but no insulation is necessary because there is no problem of sodium loss with a ceramic arc tube (such as alumina). The sleeve is held in place between a tab on the first lead wire and a terminal on the second lead wire; both lead wires are embedded in the glass stem. According to another embodiment, the sleeve is held in place by bends in the lead wires, which are welded to leads embedded in the stem.
Protected mount designs are typically quite expensive and difficult to mechanize. In addition, most mounts are insufficiently rigid and may come apart with rough lamp handling (as during transportation).